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hecoules

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  1. hecoules

    Color mapping to normals direction

    I'm arriving a bit late to the party here, but I think that this has something to do with the problems described by Lindsay MacDonald in p106 of his PhD thesis. He claims (and I'd agree) that there's an error in the original 2001 paper by Malzbender et al. - specifically that the surface normal is stated incorrectly in eq. 18. It looks as though this error has persisted into PTM fitter, and so what is reported by RTIBuilder to be the surface normal vector is actually the specular vector. This means that if you take the 'surface normals' image from RTIBuilder and apply the linear mapping described by several contributors above (i.e. [0 to 255] for [-1 to 1] for each of the three vector components), the result is out by a factor of roughly 2 (assuming that the camera is remote from the subject). Can anyone else confirm this? Maybe someone involved with fitter development can lend some insight. Looking at the results from the HSH fitter there seems to be a similar thing going on, although in that case there is no mathematical reason (that I can think of) why there should be an issue...
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